This invention relates in general to telephonic communications and more particularly relates to cellular communications via a docking station.
In recent years, the vast majority of the industrialized world has become telephonically accessible via public switched telephone networks (PSTNs). Nonetheless, there remain significant populations in rural or less developed areas who are not accessible via a PSTN for a variety of reasons relating to economy and geography. In such areas, remote communication has been accomplished by radio communications systems or cellular mobile radiotelephone (CMR) systems.
A conventional radio communications system uses a base station transceiver located at a site for favorable radio propagation and a set of transceivers typically located in remote areas. Most radio communication systems of this type are useful for conducting communications between short distances, such as within the boundaries of a town or city, via a very high frequency (VHF) radio link.
Although conventional radio communications systems are useful for specialized communications applications, two-way radios are not widely accepted for general purpose communications. In many locations, the use of two-way radios is governmentally regulated and the allocated frequency spectrum is relatively limited. Furthermore, the quality of communications is subject to the propagation conditions between communications sites. Additionally, two-way radio equipment is generally large and heavy and, as a result, is unlikely to be carried by a user at all times or to be installed in small or existing equipment.
Another form of two-way communication is a CMR system. Typical CMR systems are characterized by dividing a radio coverage area into smaller coverage areas or xe2x80x9ccellsxe2x80x9d using low power transmitters and coverage-restricted receivers. As shown in U.S. Pat. Nos. 3,906,166 and 4,268,722, the limited coverage area enables the radio channels used in one cell to be reused in another cell. As a cellular mobile radiotelephone within one cell moves across the boundary of the cell and into an adjacent cell, control circuitry associated with the cells detects that the signal strength of the radiotelephone in the just-entered cell is stronger, and communications with the radiotelephone are xe2x80x9chanded offxe2x80x9d to the just-entered cell. Thus, a CMR system can supply two-way communications for an array of cells, thereby supplying communications for a much wider area than conventional two-way radios.
Use of cellular mobile radiotelephones can pose an appreciable expense to the user. Initially, a cellular mobile radiotelephone must be purchased and an initial registration fee paid to a cellular carrier providing service to the geographic area where the handset will be used. A telephone number is assigned to the newly purchased radiotelephone and a xe2x80x9chandset I.D.xe2x80x9d is established by the carrier and maintained within the CMR system. The handset I.D. identifies communications from that particular radiotelephone as coming from a subscriber to the cellular carrier""s services.
Beyond the initial purchase and cellular carrier connection fees, expenses incurred in ordinary use of such a radiotelephone are even more significant. Historically, every communication placed from a radiotelephone is processed through the CMR system without regard for the location of the radiotelephone when the call is placed. Such processing incurs a combination of usage fees and toll or roamer charges. These fees vary depending upon the location of the radiotelephone relative to the geographic coverage area of the cellular carrier""s services subscribed to, as well as other time and geographic related variables. In a basic case, a radiotelephone user who subscribes to a cellular carrier""s services in Atlanta and who places a call from within his area of geographical coverage to a party, also located in Atlanta and within the same geographical coverage area, would be assessed a fee for accessing the CMR system, in addition to a per minute usage fee. The same call placed from a conventional telephone linked directly to the PSTN would be deemed a xe2x80x9clocal callxe2x80x9d and would typically generate no per call fees. In a more extreme case, the same subscriber to a cellular service having a geographical service area in Atlanta who is on vacation in Los Angeles and desires to use his radiotelephone to place a call from his hotel room to a restaurant across the street will incur roamer charges for accessing the CMR system outside of his carrier""s geographical coverage area, a fee for relaying the call from Los Angeles back to his carrier""s mobile switching center in the Atlanta area, a fee for relaying the call from Atlanta back to the restaurant across the street from the caller in Los Angeles, all in addition to a per minute usage fee. Again, had the subscriber placed this call from his hotel room to the restaurant across the street via a conventional telephone linked directly to the PSTN, the call would have been deemed xe2x80x9clocalxe2x80x9d and would have incurred no carrier-related fees.
Until recently, individuals in areas without direct access to the PSTN but desiring telephonic capability were essentially limited to costly and inconvenient CMR systems. Some of the inconvenience of using a home-based radiotelephone have been addressed with the advent of so-called fixed wireless (FWL) systems. FWL systems typically comprise a conventional cellular telephone physically connected to one or more conventional telephone handsets within a discrete location, such as a residence or office. The FWL system allows the connected conventional telephone handsets to access the CMR system through the cellular telephone to which they are connected. Even FWL systems, though, allow virtually no freedom of movement for the user and do not resolve other problems typically associated with CMR systems, including high cost of operation.
Accordingly, there is a need to provide individuals who do not have access to the PSTN a way to communicate telephonically in a reliable and cost-efficient manner. Additionally, there is a need to adapt current FWL systems so as to facilitate the use of such systems in conjunction with existing PSTN elements. Furthermore, there is a need to develop safeguards sufficient to prevent individuals who do not subscribe to a wireless system from gaining unauthorized access to the system, regarding both incoming and outgoing communications.
The present invention allows individuals who do not have direct access to a PSTN to communicate from, and receive communication at, their homes or another predetermined fixed location telephonically in a convenient and inexpensive manner. More particularly, the preferred form of the present invention is accomplished by utilizing a communications interface in cooperation with elements found in typical cellular mobile radiotelephone (CMR) and fixed wireless (FWL) systems. The methodology of the present invention defines the interaction of the communications interface with the CMR and FWL systems to deliver communications through a PSTN conveniently and inexpensively. More particularly, the present invention allows a conventional telephone handset to communicate through a typical cellular telephone.
The communications interface comprises three basic elements which allow communication by conventional telephone handsets through the cellular telephone. The conventional telephone handsets are connected to a Telephony Support Unit (TSU) within the communications interface. The TSU is connected to a communications interface controller (CIC) which is, in turn, connected to a Mobile Telephone Interface Unit (MTIU). These components, in combination, perform the basic functions of the communications interface.
Specifically, a subscriber to a communications system which includes the communications interface for CMR and FWL systems initiates an outgoing communication from a telephone handset connected to the communications interface. The outgoing communication is passed to the communications interface via a standard telephone cable connected at one end to the telephone handset, and at its other end to the communications interface using a connector such as an RJ-11 type.
Upon delivery of the outgoing communication, the TSU receives the outgoing communication. If communications from telephone handsets are received by the TSU simultaneously, the TSU arbitrates the communications as to priority. In other words, the TSU determines which outgoing communication to accept based on priority. Following arbitration, the TSU provides notification to the originator of one of the outgoing communications of the unavailability of the communications interface to place that communication. The TSU then forwards the remaining outgoing communication to the CIC.
The CIC is connected to the TSU and, upon completion of the functions of the TSU specified above and forwarding of the outgoing communication to the CIC, the CIC receives the outgoing communication and determines whether a cellular telephone registered for operation with the communications interface is communicatively connected to the communications interface. For one aspect of the present invention, the cellular telephone must be physically connected to the communications interface to further process the outgoing communication. Alternatively, the communications interface can determine whether the cellular telephone is within a predetermined proximate range of the communications interface. If so, the outgoing communication is processed and ultimately transmitted to the cellular telephone which, in turn, transmits the outgoing communication via the CMR system.
If the CIC determines that the cellular telephone is not in communicative contact with the communications interface, an indication as such is originated by the CIC and forwarded back through the TSU to the telephone handset to inform the user. If, on the other hand, the CIC determines that the cellular telephone is in communicative contact with the communications interface and that the cellular telephone is neither already in use nor unavailable for any other reason, the CIC processes the outgoing communication. This process appends the telephone exchange number to which the outgoing communication is directed with an identifier unique to that particular communications interface. Once appended, the outgoing communication is forwarded via a suitable communications link to the MTIU.
The MTIU includes a physical interface for connection of the cellular telephone to the communications interface. The MTIU receives the forwarded outgoing communication from the CIC and passes it to the cellular telephone via any one of a number of well known interfaces, such as an RJ-11 connector, one portion of which is connected to the MTIU, and the mating portion of which is integral to the cellular telephone.
Once the outgoing communication is received indicating that the cellular telephone is in communicative contact with the communications interface, the MTIU forwards the outgoing communication, preceded by the appended telephone exchange number to which the outgoing communication is directed, to the cellular telephone. The cellular telephone receives the outgoing communication from the telephone handset through the communications interface, and awaits a xe2x80x9csend eventxe2x80x9d recognizable to the cellular telephone as a command to xe2x80x9csendxe2x80x9d the outgoing communication. Once the xe2x80x9csend eventxe2x80x9d occurs, the cellular telephone transmits the outgoing communication to the CMR system in a well known manner.
The CMR system receives and processes the outgoing communication in the manner of conventional cellular communication. During processing, the Mobile Switching Center (MSC) recognizes the identifier appended to the telephone exchange number as indicating that the outgoing communication originated from the communications interface. In response to this recognition, the MSC directs an authentication unit to verify the origin of the outgoing communication. In response to this instruction from the MSC, the authentication unit authenticates the outgoing communication in a known manner.
One authentication method is the xe2x80x9cseed and responsexe2x80x9d type, in which the authentication unit transmits a numerical sequence to the communications interface. The communications interface, upon receipt of the numerical sequence, performs a predetermined, unique algorithmic function on the numerical sequence before transmitting back to the authentication unit the result of the manipulation of the number sequence (first manipulated number sequence). Concurrently, the authentication unit, which contains a database in which a list of subscribing communications interfaces and their unique algorithmic functions are maintained, determines the proper algorithmic function corresponding to the appendage to the telephone exchange number of the outgoing communication. The authentication unit then performs the proper algorithmic function on the same number sequence sent to the communications interface, resulting in a second manipulated number sequence.
If the authentication unit does not receive a response, or receives from the communications interface any response other than the first manipulated number sequence which matches the second manipulated number sequence, the authentication unit informs the MSC and the MSC routes the outgoing communication to its intended recipient via a telephone cable trunk allocated for use by non-users of the communications interface. If, on the other hand, the first and second manipulated number sequences match, the authentication unit indicates such to the MSC which, in turn, directs the outgoing communication to its intended recipient via a specially designated telephone cable trunk reserved for use by users of the communications interface. A record of the disposition of each authentication procedure, along with a record of which telephone cable trunk each outgoing communication was eventually routed to, is maintained within the CMR system.
Communications incoming to the CMR system are also distinguished based on whether the incoming communication is directed to a user of the communications interface. For example, telephone exchange numbers corresponding to users of the communications interface can be maintained in a database within the CMR system. Prior to forwarding the incoming communication to the selected cellular telephone, the telephone exchange number of the incoming communication is compared to telephone exchange numbers stored in the database.
If the telephone exchange number of the incoming communication corresponds to an entry in the database, the CMR system queries the cell site in which the selected cellular telephone is registered for operation as to whether the selected cellular telephone is presently located within that particular cell cite. If so, a record of the telephone exchange number of the incoming communication corresponding to the database entry, as well as the presence of the selected cellular telephone in its cell cite of registration, is created and maintained within the CMR system. Thereafter, the incoming communication is forwarded to the selected cellular telephone. This authentication can occur separately or in conjunction with an additional authentication step, such as the xe2x80x9cseed and responsexe2x80x9d type.
If, on the other hand, either the telephone exchange number of the incoming communication does not correspond to a database entry indicating use of the communications interface or the selected cellular telephone is not within its cell site of registration, a separate record to this effect is created. The incoming communication is then forwarded to the selected cellular telephone. Upon receipt of the incoming communication by the selected cellular telephone, an indication is forwarded through the communications interface to the connected telephone handsets to permit either the selected cellular telephone or any connected telephone handset to respond to the incoming communication.
That the present invention and the preferred embodiments thereof overcome the drawbacks set forth above and accomplish the advantages of the invention set forth herein will become apparent from the detailed description, the appended claims and the drawings.